Split tests, fix ToDos
Move out FatNode and Treap implementation.
More tests for Treap.
Add LCG random.
Fix bug, using random for priorities.
Random generator for debug purposes.
Enhance Treap to storing key-value pairs
Implement iterator for Map.
Ooops...
Add common Persistent trair.
Update interface for persistent structures.
Implement FatNode for undo-redo.
merge 'undoredo' into 'dlist'

Conflicts:
	src/lib.rs
	src/main.rs
visibility
option -> x, treemap -> hashmap